Lysophosphatidic acid (LPA) is an essential bioactive phospholipid mediator that regulates a range of developmental and physiological processes which are emerging as targets for a new class of molecular therapeutics. In the cardiovascular system, LPA is poised to serve as a mediator of atherothrombotic disease: it is abundant in atherosclerotic plaque, increases during acute myocardial infarction, triggers phenotypic responses in smooth muscle cells, and disrupts endothelial integrity. We and others have demonstrated that LPA promotes both the development of intimal hyperplasia following injury and atherosclerosis in experimental models. Lipid phosphate phosphatase 3 (LPP3), encoded by the PPAP2B gene, is an integral membrane enzyme that regulates the bioavailability of LPA. We have recently demonstrated that LPP3 is an intrinsic negative regulator of vascular inflammation, suppresses smooth muscle cell proliferation, and promotes endothelial barrier function likely by limiting LPA signaling. Analysis of data from a series of genome-wide association studies of coronary artery disease (CAD) identified a striking association between the PPAP2B locus and myocardial infarction. We provide evidence that CAD-risk associated PPAP2B variant disrupts an intronic enhancer that increases transcription of the gene and LPP3 expression in ox-LDL stimulated macrophages. These findings suggest the testable hypothesis that LPP3 functions as an atherosclerosis suppressor and that reduced PPAP2B gene expression aggravates cellular events underlying atherosclerosis and increases the likelihood of myocardial infarction. In this proposal, we will define the role of LPP3 in the development of atherosclerosis, provide insight into the molecular mechanism(s) involved, and validate the predicted risk allele associated with CAD in humans. We are uniquely well-prepared to achieve these goals based on our expertise in bioactive lipid signaling and the tools we have amassed to study LPP3. Completion of these studies promises to provide valuable insight into the mechanism(s) by which extracellular bioactive lipid mediators influence the development of atherosclerosis and provide novel and innovative targets to predict, prevent and treat CAD.